Rotary feed disks having angularly spaced pockets into which balls lodge when transported from a chute to a throwing machine are well-known, as is also well-known the tendency of the balls to jam against adjacent structures when an unpocketed ball is carried around on top of the disk. The object of this invention is to provide a jam-proof rotating flexible pocketed disk for receiving tennis balls from a feed chute and transporting them to an entranceway of a ball throwing machine, wherein the disk is sufficiently flexible so as to be deflected downwardly by an unpocketed ball jammed between the upper side of the disk and adjacent overlying structure, such as the feed chute. In conjunction with the disk flexibility feature it is vital that there be a clearance path through which a jammed ball may escape.